The invention relates to articles having reduced pigment swirling.
Rotomolded articles can be formed of a blend of a resin and one or more pigments. Typically, during rotomolding the blend is placed in a mold, and the mold is biaxially rotated while being heated.
During the early stages of mold rotation, a static charge can be generated. This can result in a molded article having a non-uniform color pattern, commonly referred to as pigment swirling.
Organic anti-static agents have been used to try to control pigment swirling in rotomolded articles. Often, these anti-static agents function by drawing moisture from the air to become conductive and dissipate the static charge. As a result, the ability of organic anti-static agents to reduce pigment swirling can depend upon the humidity of the environment in which rotomolding occurs. Moreover, these anti-static agents can act as mold release agents which can cause premature separation of the article from the mold. In addition, organic anti-static agents often have low melting points, so they can soften and cause agglomeration of the powdered pigment which can result in specks in the molded article.
Non-hygroscopic anti-static agents are known, and have been used in relatively high concentration to reduce static charge.